dna replication

what is dna replication?

it is the first step of cell division and it is the process by which DNA is copied during the cell cycle

where does dna replication take place in the cell?

the nucleus

what stage is dna replicated?

s phase

what is the point of dna replication?

so that every cell will have a complete set of DNA

what is the structure of a deoxyribonucleotide?

it has a phosphate group attached to a 5 carbon sugar, it has a hydroxyl group attached to the 3 carbon sugar, and it has a base that can consist of either adenine, thymine, guanine, or cytosine

what direction does dna replication occur in?

5 - 3 direction only

what links deoxyribonucleotides?

phosphodiester bonds

what is the difference between sugar deoxyribose and sugar ribose?

the sugar deoxyribose contains one more hydroxyl group (OH)

what are the hydrogen bond pairs?

T and A; C and G

why is dna replication not mRNA?

because dna replication contains thymine and RNA contains uracil

what does semiconservative mean?

it is a process by which an original DNA replicates itself to produce two similar copies

why is semiconservative in dna replication important?

because it allows cells to make accurate copies of DNA

what is the origin of replication?

it is the starting point of replication and it is where enzymes and proteins bind and separate the DNA strands in preparation for replication

what is the replication fork?

it is when the double helix unzips and once it starts to separate it forms a bubble and this is when dna replication takes place

what is replication bubble?

it is when the DNA the bubble widens and replication occurs in both directions. the new DNA strands are visible and pair with the separated og strands in the bubble

what are the three different time points of dna replication?

time one - origin of replication, time two - replication fork, and time three - replication bubble

what are the steps for dna replication?

step one is to open up the DNA double helix for copying, the dna helicase will open and unwind the DNA. step two is to prevent basepairing and the dna breaks. the topoisomerase relieves stress to prevent the backbone from breaking. step three is to replicate the dna. the primase proves a primer to start and continue towards the fork

what is primase?

it is an enzyme that synthesizes short RNA and are called primers

what does dna polymerase need for dna polymerization?

it needs a free 3’ -OH group

what are leading strands?

they are continuous dna synthesized strands that move towards the fork

what are lagging strands?

they are discontinuous dna synthesized strands that move away from the fork

what are okazaki fragments?

they are small fragments that are the lagging strands in DNA molecules and need primer to fill the gaps in between the fragments

what is dna ligase?

it is an enzyme that acts as the glue to join DNA fragments together

what is a replisome?

it is a complex structure that contains all replication machinery

what are telomeres?

they are the protective caps at the end of the chromosomes to prevent the DNA from damage

what does telomerase do?

it is an enzyme that helps maintain the telomeres by extending them and it maintains the ends of eukaryotic chromosomes

what happens to the telomeres in telomerase?

the longer the cells divide the telomeres get progressively shorter

what is telomerase in cancer cells?

they are hyperactivated